Vasodilation is a term that describes the increase in the internal diameter of a blood vessel that results from relaxation of smooth muscle within the wall of the vessel. Vasodilation can cause an increase in blood flow, as well as a corresponding decrease in systemic vascular resistance (i.e., reduced blood pressure). Tissue perfusion is a term that generally describes blood flow into the tissues.
Vasodilation has been recognized to be beneficial in the treatment of myocardial infarction, strokes, and vascular diseases.
Maintaining adequate tissue perfusion is recognized to be beneficial during any hypoperfused event, during any coronary syndrome including myocardial infarction, before, during, or after medical intervention (e.g., angioplasty, plastic and reconstructive surgery, maxillofacial surgery, vascular surgery, transplant surgery, or cardiac surgery); or before, during, or after dental procedures, or dermatological test patches and other skin challenges, or before, during, or after an exercise regime; or during wound healing.
The effects of ultrasound energy upon enhanced vasodilation and/or blood perfusion have been observed. However, the conventional use of ultrasound energy in medicine for either diagnostic or therapeutic purposes typically has involved the application of ultrasound energy at frequency ranges—e.g., about 2 MHz to 40 MHz for diagnostic purposes (ultrasound imaging), and about 1 MHz to 3 MHz (physiotherapy or diathermy devices)—and/or with attendant exposure times, that can induce thermal effects due to tissue absorption of ultrasound energy. These thermal mechanisms caused by tissue absorption of ultrasound energy can lead to substantial deep heating of tissue. Often, in typically conventional ultrasound modalities, the thermal mechanisms due to absorption of ultrasound energy in tissue can be intended and beneficial, or at least not detrimental. However, when the principal purpose of the therapy is to create vasodilation and/or sustain adequate tissue perfusion in instances where the body is undergoing, or is about to undergo, or has undergone an event that is or has the potential for challenging patient well being, unintended substantial deep tissue heating effects or other unnecessary physiologic challenges to body tissue or organs should be avoided.